1. Field of the Invention
The present invention relates to multicolor ink jet printers of the continuous type and more particularly to cooperative ink cartridge and printer housing constructions which assure that different ink supplies are coupled to different color ink circulation systems with the proper ink-color relation.
2. Background Art
In continuous ink jet printing apparatus streams of uniformly spaced ink drops are created by imposing predetermined vibrations upon liquid ink filaments issuing from an orifice plate. The filaments are formed by supplying ink under pressure to a print head cavity that is in communication with the orifice plate. Information is imparted to the droplet streams by selective non-charging or charging and deflection of droplets. A portion of the droplets pass to the recording medium but there are a substantial number of non-printing droplets that are intercepted by a catcher for recirculation. Often the print head cavity has an outlet other than the orifice plate (e.g. to facilitate dynamic pressure control within the cavity at start-up), and the apparatus ink supply system also circulates such ink flow. In many applications there are a variety of other fluid couplings to the ink reservoir that may be useful.
U.S. Pat. No. 4,591,875 discloses a highly useful ink-cartridge/printer-housing system which enables convenient and cleanly replenishment of the ink supply to such printers, by casual operators in contrast to service specialists. In general, this system provides: (i) an ink cartridge having a plurality of parts (e.g. ink supply and ink return ports), each having valve elements that are biased to a closed condition, and (ii) a printer-housing having a corresponding plurality of ink circulation system terminals that are biased to a closed condition. The cartridge valves and housing terminals are mutually actuatable to an open condition by engaging movements of a cartridge being inserted into the housing.
The replaceable ink cartridge approach of the above noted U.S. Pat. No. 4,591,875 can be used in printer systems having multicolor printing capabilities. For example, a continuous ink jet printer can have a plurality of separate ink circulation systems respectively handling a plurality of different ink jet print heads that print respectively with different ink colors. From the viewpoints of printer simplicity and economy of manufacture, it is highly desirable that the ink cartridges and printer housing constructions of such discrete different color ink circulation systems be identical. This allows the same operator function for replacement of each ink color and minimizes the number of different kinds of parts to be fabricated and assembled.
However, a potential problem has been observed in the use of such a multicolor ink cartridge printer. Specifically, an operator has the capability to insert an ink cartridge of one color into cooperation with the circulation system for a print head of another color ink. This can have a relatively disasterous effect, viz. the mixing of different ink colors, and must be remedied before further printing can proceed, by a service call to remove, or completely purge, the contaminated ink circulation system.